The invention relates generally to apparatus for enabling continuous operation of power supplies during transient fault conditions. More specifically, the invention concerns a storage element for a step-up or boost voltage regulator which is switchable between the regulator input and output depending upon the location of the transient fault.
Known DC power supplies use an energy storing element, such as a large capacitor, across the output. This so-called "hold-up" capacitor serves as a compensating device for load changes and as an energy source for the load for use during a transient line fault condition. The capability for maintaining the power supply output to the load within a specified tolerance during a faulty line condition is important, for example, in computer system power supply applications where it is desired to transfer data in volatile memory to a non-volatile storage device during the transient condition in case the power supply problem persists to the point where the computer system would have to be shut down. The longer the hold-up time required, the larger the required capacitance. Large capacitor banks are expensive and take up excessive physical space in the power supply housing equipment.